The invention relates generally to brominated derivatives of poly(2,6-dimethyl-1,4-phenylene oxide) and, more specifically to membranes formed of the new compounds that have improved mechanical and CO2-separation properties.
Poly(2,6-dimethyl-1,4-phenylene oxide) (PPO for short) is known to be a membrane material that has high CO2 affinity, and hence high CO2 permeability (Chowdhury, G.; Kruczek, B.; Matsuura, T. (Eds.), Polyphenylene Oxide and Modified Polyphenylene Oxide Membranes; Gas, Vapor, and Liquid Separation, Kluwer Academic, 2001, 105-145; He, Z.; Pinnau, I.; Morisato, A. Desalination 2002, 146, 11-15; Chowdhury, G.; Vujosevic, R.; Matsuura, T.; Laverty, B. J. Appl. Polym. Sci. 2000, 77, 1137-1143; Hamad, F.; Khulbe, K. C.; Matsuura, T. J. Memb. Sci. 2005, 256, 29-37; Khulbe, K. C.; Chowdhury, G.; Matsuura, T.; Lamarche, G. J. Memb. Sci. 1997, 123, 9-15). PPO properties can be improved by chemical modification. For example, Story et al. reported that substituting the aromatic ring with bromine groups can increase the CO2 permeability as much as 2.5 times without sacrificing its selectively (Story, B. J.; Koros, W. J. J. Memb. Sci. 1992, 67, 191-210). Hamad et al. further improved the CO2 selectivity relative to CH4 by introducing a sulfonic acid group to the brominated PPO at the ring position (Hamad, F.; Matsuura, T. J. Memb. Sci. 2005, 253, 183-189).
One of the PPO derivatives that has not been explored yet as a CO2 membrane material is poly(2,6-diphenyl-1,4-phenylene oxide) (DPPPO). DPPPO was synthesized by Hay et al. in the 1960's (Hay, A. S. Macromolecules 1969, 2, 107-108). DPPPO easily crystallizes with a Tm of about 470° C., which is near its decomposition temperature, which will adversely impact its processing and mechanical properties (Yang, H.; Hay, A. S. J. Polym. Sci. 1993, 31, 1261-73). Preferred embodiments of the present invention are focused on other PPO modifications, such as brominated DPPPO and nanoparticle-containing DPPPO.